Default props for mail template previews

[Josh-Walker-GM]

Currently, when you visit a template preview you get a placeholder value that simply shows the prop keys that we managed to work out from your template files.

Feedback here from the community highlights that it is kind of a pain to have to retype in many prop values to get the template to render.

Perhaps we could add some expected named export (defaultProps) which contains a list of default props. We would then use them as the defaults allowing the mail template to render immediately rather than fail given the lack of props.

[dthyresson]

I noticed this when demoing — as the value of props changes can get GraphQL errors with malformed JSON.

Might need to denounce on set not on change but add a submit.